1. Field of the Invention
The invention relates to an optoelectronic device and more particularly to a structure of an image sensor device and a method for fabricating the same.
2. Description of the Related Art
As optoelectronic applications, such as digital cameras, digital video recorders, image capture capable mobile phones and monitors, become more and more popular, the demand for image sensor devices accordingly increase. An image sensor device is used for recording a photo signal from an image and converting the photo signal into an electronic signal. After recording and processing the electronic signal, a digital image is generated. In general, image sensor devices can be categorized into two main types, one is charge coupled devices (CCD) and the other complementary metal oxide semiconductor (CMOS) devices.
FIG. 1 shows a cross section of a conventional CMOS type image sensor device 10. The image sensor device 10 typically comprises a pixel array formed on a silicon substrate 100. Each pixel includes a photo-conversion device 101, such as a photodiode, formed within the corresponding pixel region of the silicon substrate 100, so as to produce a signal corresponding to the intensity of light impinging thereon. Here, only four pixel regions 100a, 100b, 100c, and 100d are depicted. When a light source is focused on the array, signals can be employed to display a corresponding image. A microlens array 106 is correspondingly disposed above the pixel array and used for focusing light onto the pixel array. A color filter array 104 is correspondingly interposed between the pixel array and microlens array 106. Each color filter allows light with particular wavelengths to pass the respective photo-conversion device 101. An intervening layer 102 is between the color filter array 104 and the silicon substrate 100, which includes interconnections (not shown) to form electrical connection between the devices of the pixel array and between the pixel array and the peripheral circuit (not shown) of the pixel array.
However, a large amount of incident light (not shown) is reflected from the silicon substrate 100 and cannot be absorbed efficiently by the photo-conversion devices 101 due to the smooth surface of the silicon substrate. Thus, the intensity of the incident light to each pixel/photo-conversion device is reduced. The reduced light intensities may enhance cross-talk of pixels, resulting in reduction of the signal to noise ratio (SNR) and photosensitivity of the image sensor device.
Therefore, there is a need to develop a novel design for a pixel array capable of enhancing quantum efficiency of pixels and reducing cross-talk of pixels.